E. Lillethun

Production spectra of π±, K±, p± at large angles in proton-proton collisions in the CERN intersecting storage rings

Abstract Results are given on the inclusive production of charged pions, kaons, and nucleons, in proton-proton collisions at c.m. energies from √ s = 23 to 63 GeV at large angles and for the transverse momentum range 0.1 p T c . The dependence of the production spectra on the collision energy √ s , the transverse momentum p T , and the longitudinal rapidity is discussed.

Evidence for gluon bremsstrahlung in e+e− annihilations at high energies

Abstract We report our results on the reactions e+e− → hadrons in the energy range 13 ⩽ Ecm ⩽ 31.6 GeV and compare them with qq jets described in the quark-parton model and with first-order QCD predictions including gluon emission (qqg jets). At high energies the observed features of one-sided jet broadening, sea-gull effect and planar events with a three-jet structure represent a gross violation of the parton model without gluons and find a most natural interpretation if gluon bremsstrahlung is included.

The Production of Charged Particles with High Transverse Momentum in Proton-Proton Collisions at the CERN ISR

Results are given on the inclusive production of charged pions, kaons and nucleons in high-energy proton-proton collisions in the centre-of-mass rapidity range |ycm| < 1 and for transverse momenta up to 4.8 GeV/c. The dependence of the composition of produced particles on ycm, the total energy s, and transverse momentum pT is discussed.

Production of high transverse momentum particles in p-p-collisions in the central region at the CERN ISR

Abstract The inclusive production al all charged particles of transverse momentum p T between 1.5 and 4.4 GeV/ c at centre of mass angles 90° and 59.4° from p-p-collisions with √ s = 44 and 53 GeV has been measured. No strong energy dependence is observed for these transverse momenta.

Multiplicity Distributions in e+ e- Annihilations at PETRA Energies

Abstract Measurements of the charged multiplicities for hadron production in e+e− annihilation in the center of mass energy range 9–32 GeV have been made. The average charged multiplicity has an energy dependence much stronger than ln s and similar to that reported for pp collisions. Quantitative differences are observed in the magnitude of both the average multiplicity 〈nch〉 and the dispersion Dch for e+e− and pp interactions at the same center of mass energy. 〈nch〉 and the ratio 〈nch/Dch in e+e− annihilations are significantly larger than in pp collisions and are found to be in overall agreement with QCD predictions. KNO scaling is seen to be satisfied.

First observation of hadron production in e+e− collisions at 13 and 17 GeV CMS energy with the pluto detector at petra: Pluto Collaboration

Abstract First results from the magnetic detector PLUTO at the new e + e − storage ring PETRA are shown. The ratio R of the cross section for hadron production to that for μ-pair production has been measured to be R = 5.0 ± 0.5 at 13 GeV and 4.3 ±0.5 at 17 GeV. Both values have an additional systematic error of 20%. The events show a typical 2-jet structure. The mean transverse momentum approaches a constant value with increasing energy implying a shrinkage of the jet opening angle.

Cross-Sections and Event Topologies in e+ e- Annihilation at 13-GeV and 17-GeV Observed with the PLUTO Detector

Abstract First results from the magnetic detector PLUTO at the new e + e − storage ring PETRA are shown. The ratio R of the cross section for hadron production to that for μ-pair production has been measured to be R = 5.0 ± 0.5 at 13 GeV and 4.3 ±0.5 at 17 GeV. Both values have an additional systematic error of 20%. The events show a typical 2-jet structure. The mean transverse momentum approaches a constant value with increasing energy implying a shrinkage of the jet opening angle.

Studies of proton-proton collisions at the CERN ISR with an identified charged hadron of high transverse momentum at 90°: (II) On the distribution of charged particles in the central region

Abstract Results are reported from an investigation of proton-proton collisions at a c.m. energy of 52.6 GeV, in which a charged hadron with large transverse momentum is produced near 90° in the c.m.s. We have studied the momentum and charge correlations between identified high- p T trigger particles and other charged particles in the central region (rapidity | y | p T particles with charge opposite to that of the trigger particle in a small solid angle around the trigger particle. The sum of the momenta of charged particles inside | y | c per GeV/ c increase of the trigger momentum. Opposite in azimuth to the trigger particle we observe close pairs of high- p T particles in both neutral and doubly charged combinations. In this region we see an indication of scaling in the x E variable for trigger momenta exceeding 3 GeV/ c . The distribution of charge is strongly correlated with the charge of the trigger particle. Otherwise the type of trigger particle does not affect strongly the observed event structure, but for trigger momenta above 3 GeV/ c , K − and p triggers are observed to have fewer negative high- p T recoil particles within | y |

Large angle production of stable particles heavier than the proton and a search for quarks at the CERN intersecting storage rings

Abstract Measurements have been performed on production of particles with mass 1.5 GeV/c2 and charge ⩾ 2 3 for θlab = 62.5° and s = 53 GeV . At pT = 0.7 GeV/c the relative rate of production of antideuterons to π− is (5 ± 1) × 10−5. The deuteron to antideuteron ratio is 3.7 ± 1.2. No new stable particle has been amongst 0.7 × 108 charged particles entering our detector.

Large-angle inclusive production of charged pions at the CERN ISR with transverse moment a less than 1.0 GeV/c

Abstract The inclusive production of π ± in proton-proton collisons has been measured for the transverse momentum range 0.15 to 1.0 GeV/ c over an angular range of 29° to 89° in the centre-of-mass system and for centre-of-mass energies √ s = 30.6 and 52.8 GeV. For each energy the invariant cross-section foe fixed transverse momentum was found to increase by about 15% as the centre-of-mass rapidity decreases from 1 to 0, i.e. the “central plateau” has not yet been reached.